Action: Amphibians: Provide natural substrate for species which do not breed in water (e.g. burrowing/tunnel breeders)
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- Two replicated studies in Australia and Fiji found that adding a variety of substrates to an enclosure, as well as rotting logs and hollow bamboo pipes in one case, promoted egg laying in frogs. The Australian study also temporarily flooded enclosures, manipulated sex ratios and played recorded mating calls.
Breeding may be stimulated by promoting natural breeding behaviours, such as digging or nest building. By providing natural substrate, which may be present in the amphibian’s wild environment, natural digging and building behaviour may be triggered, leading to breeding.
Supporting evidence from individual studies
A replicated, before-and-after study in 1994–1996 of roseate frogs Geocrinia rosea at Melbourne Zoo, Australia found that frogs only bred after being moved to an indoor enclosure which had a mix of organic substrates, temporary flooding of enclosures, manipulated sex ratios, introducing females carrying eggs to males, and recorded mating calls being played. The only fertile spawning occurred in spring 1996, in a well-established burrow hidden beneath dry leaf litter and eucalyptus bark which contained 25 eggs, but they were later destroyed by fungus. From 1994-1995 , two male and three sub-adult frogs were housed in two outdoor tanks (120 x 60 x 60 cm) with a sub-surface water depth 50-100 mm. Males called when they were in outdoor enclosures, but fertile eggs were not produced until animals were moved to indoor tanks. From 1996, 6–7 frogs were housed in each of four indoor tanks (47 x 55 x 36 cm and 180 x 46 x 46 cm) with moss, mud, bark and palm peat as substrates.
A small, replicated, before-and-after study in 2004-2007 in Fiji found that the provision of egg laying sites including various organic substrates, rotting logs and hollow bamboo stems Piper aduncum in an enclosure resulted in successful breeding for two pairs of Fijian ground frogs Platymantis vitianus. A total of 39 froglets were raised after one year. Two egg clutches were found, one in a section of bamboo stem filled with damp soil substrate, and another under a moist rotting log on a mix of soil and leaf litter. A captive breeding program had been running for this species since 2004, but only one froglet was reared after three years of trying. From 2006-2007, five male and five female frogs were placed in a purpose built outdoor enclosure. Further detials: Narayan E, Christi K. & Morley C. (2009) Captive propagation of the endangered native Fiji-an frog Platymantis vitiana: Implications for ex-situ conservation and management. Pacific Conservation Biology, 15, 47–55.
- Birkett J., Vincent M. & Banks C. (1999) Captive management and rearing of the roseate frog, Geocrinia rosea, at Melbourne Zoo. Herpetofauna, 29, 49-56
- Narayan E., Christi K. & Morley C. (2007) Provision of egg-laying sites for captive breeding of the endangered Fijian ground frog Platymantis vitianus, University of the South Pacific, Suva, Fiji. Conservation Evidence, 4, 61-65